A typical hand hoist comprises a planetary spur gear design and includes a handchain wheel with an endless handchain that drives a gear reduction through a Weston type mechanical load brake. The gear reduction in turn drives a load sheave or load wheel to which the load chain with hook is fitted. Pulling on one side of the endless handchain with sufficient force will raise the load hook and the load. Pulling on the opposite side of the handchain will lower the load hook.
Because competitive conditions require that hand hoists be relatively inexpensive and at the same time give long service under adverse conditions, in fact, users frequently overload hoists. The resulting wear under such conditions is excessive and a hazard to life and property.
As a hoist in many installations is available to anyone on the floor who wishes to use it and many who have only occasional need for it are ignorant or indifferent to the limitations of its use, it would seem desirable to arrange a hand hoist so that it cannot be abused by overloads engendered by attempts to lift large weights or by various faulty practices which produce excessive and unsafe stresses on the hand hoist.
The desirability of a load limiting device has long been recognized in connection with the hand hoist.
It is an object of the present invention to provide a hand hoist which will not lift any load beyond a predetermined maximum load; and wherein overloading of the hand hoist does not interfere with the normal operation of the hand hoist.